let list = [1, 2, 3, 4]
let obj = { "a": 1, "b": 2, "c": 3 }
for (let k in list) {
    console.log("循环遍历数组中in中的k是下标", k)
}
for (let k of list) {
    console.log("循环遍历数组中of中的k是值", k)
}
for (let k in obj) {
    console.log(typeof k)
    console.log(k)
}